Environmental Manipulations for Captive Lahontan Cutthroat Trout Increase Hatchery Egg Survival and Survival of Yearlings Stocked in Saline, Alkaline Walker Lake, Nevada PDF Download

Author: John P. Bigelow
Publisher:
ISBN:
Category : Thesis
Languages : en
Pages : 158

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Book Description
I investigated the reproductive temperature requirements of captive Lahontan cutthroat trout (Oncorhynchus clarkii henshawi ) brood females, and various acclimation protocols for yearling, hatchery-reared Lahontan cutthroat trout stocked in saline, alkaline Walker Lake, Nevada Survival of eggs to the eyed developmental stage, hatching, and yolk-sac resorption was higher when spawned from brood females held in chilled water (7.2°C) from mid December through spawning compared to eggs spawned from females on ambient well water (12.4°C) regardless of whether females were spawned 0, 4, or 7 d post ovulation. Female holding temperature did not appear to affect the timing of ovulation; however, fecundity was higher for females held at 7.2°C versus 12.4°C. The hazard of mortality during a week-long challenge in water from Walker Lake, Nevada for eight-month-old Lahontan cutthroat trout reared at Lahontan National Fish Hatchery was lower for fish acclimated 3 and 8 d by gradually increasing the ratio of lake water to hatchery water compared to un-acclimated fish. Increased fork length also reduced the hazard of death. No fish survived the entire week-long challenge, indicating improvements in the acclimation method are necessary. In a second acclimation study, the hazard of mortality for yearling, hatchery-reared Lahontan cutthroat trout during three replicate week-long challenges in saline, alkaline water from Walker Lake was lower for fish acclimated for 17 d at the hatchery in simulated lake water than for un-acclimated fish; however, acclimation for 8 d seemed to have no effect. Fish condition factor and fork length were directly correlated to challenge survival. Blood plasma osmolality was elevated in fish not surviving the challenge; however, challenge survivors that had been acclimated for 17 d exhibited normal plasma osmolality. These results will facilitate the recovery of Lahontan cutthroat trout in the Truckee-Tahoe and Walker subbasins.